Balance 30 L2TP, through Asus router

Having issues routing L2TP access to a Balance 30 for Remote User Access. It works locally on the LAN side, so I suspect routing issues through my Asus router.

I have opened 4500 and 32015, and verified that Speedfusion / Pep VPN is working.
Also opened 500 and 1701 for L2TP, but is just times out when trying to connect outside the LAN.

Asus router in question is the AC5300.

Any tips would be greatly appreciated.